This invention relates generally to a computerized tomographic apparatus; relates more specifically to an X-ray computerized tomographic apparatus utilizing a Scanography operation prior to the CT scanning operation.
Within recent years it became well known in the medical diagnostic field to employ an X-ray type computerized tomographic apparatus utilizing so-called "SCANO graphic image" taken prior to the normal "computerized tomographic image".
In X-ray computerized tomographic apparatus (referred to "CT apparatus" hereinafter) of the third and subsequent generation types, i.e., "fan beam type" X-ray tomographic apparatus, a patient is subjected to the Scanographic scanning operation prior to the CT scanning operation, to specify or determine a tomographic scanning portion from the displayed X-ray image. For the Scanographic scanning operation, an X-ray tube and an X-ray detector array of the X-ray CT apparatus are arranged to the fixed (stationary) position, and a patient couch on which the patient is laid is translated along the longitudinal axis thereof between the X-ray tube and the X-ray detector. Under this condition, X-rays are irradiated toward the patient in synchronism with the movement of the patient couch. A Scanographic image thus obtained is equivalent to an ordinary X-ray penetration type two-dimensional image.
The CRT display unit of the X-ray CT apparatus displays on the screen simultaneously the Scanographic image and "horizontal lines" equidistantly arranged for indicating possible tomographic scanning portions. After seeing the Scanographic image, an operator specifies tomographic scanning portions and keys in given numbers which, for example, could be displayed in the vicinity of the left corner on the screen aligned in the vertical direction. After this key-in operation, the patient couch is translated to position the designated tomographic scanning portion directly under the X-ray tube. Then the X-ray CT apparatus begins scanning the patient in a rotary manner.
However, the conventional X-ray CT apparatus is restricted to designate CT scanning portions of the patient by way of a plurarity of the above-mentioned "horizontal lines" of which intervals between the succeeding horizontal lines are predetermined, i.e., cannot be adjustable. In particular, when a plurality of tomographic scanning portions are required to be scanned, these portions must be specified for every individual scanning operation. Thus, the scanning operation by the conventional apparatus is troublesome and time-consuming.
Accordingly, an object of the present invention is to provide an X-ray computerized tomographic apparatus which first can designate CT scanning portions on the Scanographic image with free-adjustable "horizontal lines", and secondly can automatically perform the positioning of the X-ray irradiation toward the object for CT scanning on specified portions of the Scanographic image in a predetermined order.